Tahafut_al-Tahafut-transl-Engl-van-den-Bergh

sequences such as the eternal sequence of fathers and sons would not
form a causal series. God would not be a first cause but the Only Cause of
everything. It is the contradiction in the idea of an eternal creation which
forms the chief argument of Ghazali in this book. In a later chapter, for
instance, when he refutes Avicenna’s proof for God based on the
Aristotelian concepts ‘necessary by itself’, i.e. logical necessity, and
‘necessary through another’, i.e. ontological necessity, in which there is
the usual Aristotelian confusion of the logical with the ontological,
Ghazali’s long argument can be reduced to the assertion that once the
possibility of an infinite series of causes is admitted, there is no sense in
positing a first cause.
The first argument is as follows. If the world had been created, there
must have been something determining its existence at the moment it was
created, for otherwise it would have remained in the state of pure
possibility it was in before. But if there was something determining its
existence, this determinant must have been determined by another
determinant and so on ad infinitum, or we must accept an eternal God in
whom eternally new determinations may arise. But there cannot be any
new determinations in an eternal God.
The argument in this form is found in Avicenna, but its elements are
Aristotelian. In Cicero’s Academics we have a fragment of one of
Aristotle’s earlier and more popular writings, the lost dialogue De
philosophia, in which he says that it is impossible that the world could ever
have been generated. For how could there have been a new decision, that
is a new decision in the mind of God, for such a magnificent work? St.
Augustine knows this argument from Cicero and he too denies that God
could have a novum consilium. St. Augustine is well aware of the difficulty,
and he says in his De civilate dei that God has always existed, that after a
certain time, without having changed His will, He created man, whom He
had not wanted to create before, this is indeed a fact too profound for us.
It also belongs to Aristotle’s philosophy that in all change there is a
potentiality and all potentiality needs an actualizer which exists already. In
the form this argument has in Avicenna it is, however, taken from a book
by a late Greek Christian commentator of Aristotle, John Philoponus, De
aeternitate mundi, which was directed against a book by the great
Neoplatonist Proclus who had given eighteen arguments to prove the
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